Process of vulcanizing rubber



Patented Oct. 17, 1933 UNITED STATES- Y PROCESS OF VULCANIZING'RUBBER Robert L; Sibley, Nara, w. Va., assignor to The Rubber Service Laboratories Company, Akron,

Ohioj'a corporation of Ohio No D rawing. Application September 25, 1951/; Serial No. 565,193. Renewed January 6, 1933 32 Claims.

The present inventionrelates to the vulcanization of rubber by a new and improved process wherein a new type ofrubber vulcanization accelerator is employed. The manufacture and means of employing the preferred new class of rubber vulcanization, accelerators are fully set forth hereinafter and will be readily understood from the following description and examples of a preferred mode of carrying out the invention.

The preferred new class of accelerators comprise a reaction product of an organic base and a mercaptoarylthiazole, further reacted'with an organic acid halide. The preferred class of compounds have been incorporated alone in a rubber mix as arubber vulcanizationaccelerator,

but have been employed preferably in conjunction with a basic organic nitrogen-containing accelerating compound, for example, diphenylguanidine, as a component of a mixed accelerator. The following is one example of a preferred method of manufacturing one of the new class of accelerating compounds, comprising a phthalyl,

chloride derivative of the reaction product of mercaptobenzothiazole and hexa-methylene-tetramine: Substantially one molecular proportion (140 parts byweight) of hexa-methylene-tetramine and substantially one and one-half molec-' ular proportions (249 parts by weight) of mercaptobenzothiazole were placed in a suitable vessel and the temperature gradually raised to approximately 135 C., while agitating the mixture. The product thus formed was further reacted with a comparatively small excess over one-half above was incorporated in the usual manner ina so-called pure gum rubber stock comprising Parts Pale crepe rubber 100 Zinc oxide 5 Sulfur v 3 Stearic acid .1

The reaction product of substantially one-, half a molecular proportion of phthalyl chloride and substantially onemolecularproportion of the mercaptobenzothiazole derivative of hexa-methylene-tetramine g 1 The'rubber. stock thus compounded then cured in the usual manner by heating inya press for difierentperiods oftime at the temperature given by 30 poundsof steam pressure persquare inch. j The vulcanized rubber product on testing was found to possessthefollowingtensile and modulus characteristics:

istics when employed in the vulcanization process in the manner described. 5 o

The product described above has also been employed in a rubber stock'in conjunction with diphenylgfuanidine, and the mixed accelerator thus I formed was found to possess increased accelerat ing properties when employed in the vulcanization process. v

Another-example of the preferred class of compounds was prepared in a manner analogous to thatdescribed above, except that a comparatively small excess over one molecular'proportion (250 pa'rts'by weight) of phthalyl chloride was 'em-.

ployed in this case, the proportions of the other reactants being substantially the same as in the The above data show that the product'described I above possesses desirable accelerating characterprevious example. The product formed "was a The reaction product of substantially one] molecular proportion of phthalyl chloride and substantially one molecular proportion l, of the mercaptobenzothiazole derivative of v hexa-methylene-tetramine L 1 The stock thus formed was cu red in the usual manner and the product after curing was tested I mercaptobenzothiazole s0" to determine its modulus and tensile properties. The results followz] Table II Modulus of elasticity Cure in lbs/i11 at elongations 0f Tensile Ulnatbreak mate in eltonga- Steam lbs/in EY}?? pressure 300% 500% 700% percent lbs.

These figures show that the acceleratorabove 7 described also shows desirable properties when employed in a rubber mix.. p

The reaction product of substantially one molecular proportion of phthalyl chloride and substantially one. molecular proportion of ,the mercaptobenzothiazole derivative of hexa-methylenetetramine was also employed inconjunction with a. basic organic nitrogen-containing accelerator, for example, diphenylguanidine. ,Thus,;a rubber stock was compounded comprising- Parts Palecrepe rubber e 100 Zinc oxide 5 Sulfur V 3 Diphenylguanidine 0.6 The reaction' product of substantially one molecular proportion of phthalyl chloride and substantially one molecular proportion of the mercaptobenzothiazole derivative of hexa-methylene-tetramine 0.4

The rubber mix, after vulcanization, exhibited themodulus and tensile characteristics indicated in Table III.

Table III Modulus of elasticity Cure in lbs/in at'elonga- 5 of Tensile Egg V atbiil leak I I fiStcam v, lbs/in Ion 5 g i pressure 300% 500% 700% WW 45 20 198 480 2020 4050 830 60- 20 237 616 2500 4565. 820 90 I 20 259 691 2835 I 4400 700. r

The dataset forth in Table III show that the accelerator employed is particularly valuable in effecting the cure of a rubber product, especially when employed in conjunction with a basic organic nitrogen-containing accelerator, for example, diphenylguanidine. 0,

Another of the preferred class of accelerators,

for example, the reaction productlof substantially one molecular proportion of benzoyl chloride and substantially one molecular proportion of the derivative of hexamethylenetetramine, was prepared in a manner analogous to that described above for the prepa ration of thereaction product, of substantially one-half a molecular proportion of phthalyl chlo-' ride and substantially one molecular proportion of the mercaptobenzothiazole derivative of hexa- 'methylenetetramine, except that during and after the addition of the benzoyl chloride, the reaction temperature was maintained: at. approxi: mately 105 to 120 C. v

A portion of the accelerator just described was rAfter vulcanizing the rubber stock thus compounded, the cured rubber product was found to possess the tensile and modulus characteristics a set forth in Table IV.

Table IV 7 Modulus of elasticity Cure in lbs/in at elongav im Tensile 3,15,; a gg eli ngza- -Steam H lbs/in i g gi i preisure' 300% 500% 700% peacent I v This accelerator was also compounded in a similarrubber stock in conjunction with diphenyl- The stock was cured, and on testing found E5 possess the following characteristics:

Table V Modulus of elasticity Cure in lbs/in at elongations of Tensile atlgrleak Steam lbs/in $53 p llsosure 300% 500% 700% l The results set forth in Tables IV and'VV show that the reaction product of benzoyl chloride and the mercaptobenzothiazole derivative of hexa, methylene-tetramine possesses very desirable ac l..

celerating properties, when employed in the vulcanization of rubber. erties are markedly increased when employed in conjunction with a basic activatoras for example diphenylguanidine.

Another of the preferred class. :of compounds,

for examplethe reaction product of substantially one molecular proportion of acetyl chloride and substantially one molecular proportion of the mercaptobenzothiazole. derivative of hexa-' methylene-tetramine, was prepared in a manner analogous to that described above for the preparation of the reaction product of substantially one-half a. molecular proportion of phthalyl chloride and substantially one molecular pro- These accelerating propcompounded in the usual manner in a rubber stock comprising 1 I Parts Pale crepe rubber 10 Zinc oxide '5 Sulfur 3 Stearic acid 1 The reaction product of benzoyl chloride an the mercaptobenzothiazole derivative of -hexa-methylene-tetramine 1 [AIM portion of the mercaptobe'nzothi'azole derivative; of 'hexa-methylene tetramine; except that-after the addition of the "acetyl chloride, thereaction temperature 'was' maintained at approximately 100 to 110 C.-, preferably for a period of approximately three to four hours; The product thus obtained wasincorporated in arubber stockcom prising a I The reaction'product of "acetyl chloride and themercaptobenzothiazole derivative of" hexa-methylene-tetramine 1- This rubber stock was cured in theus'ual manner. and tested to determine itstensile and modulus The reactionproduct 5555155 11 chloride andthe ;mercaptobenzothiazole derivative of hexa-meth ylene-tetramine was also employed in conjunction with diphenylguanidine in the tollowing rubber composition: 7 v

Zinc oxide 5 Sulfur g 3 Stearic acid u 1' I Diphenylguanidine ,=0.2

The reaction product of acetyl chloride nd the mercaptobenzothiazole drivative of hxa-rnethylene-tetramine. n; 0.8

The rubber stock thus prepared was" cured tested, and the vulcanized productjvas found to possess the following physical properties:-

Table VII Modulus of elasticity A Cure in lbs/in at elonga- A tions 0! 7 7 1 11 gg J V I vatlgleak g Steam lbs/in 1 2 -1 31 pressure 300% 500% 700% V percent lbs. 7

' 30 so ,346 i 1010 4175 5140 745.

45 so 262 1 1050 4530- 4880 730 so 30 23s 1015 4530 4800 715 Tables VI and VII show that the accelerator employed possesses the desirable accelerating properties of the preferred class of compounds, which accelerating properties are increased when employed in conjunction with a basic activator accelerator. 1

Another example of the preferred class of accelerators, comprising a reaction product of phthalyl chloride and the mercaptobenzothiazole derivative of acetaldehyde-ammonia, was pre- 1 pared as follows: .Substantially. one. molecular proportion; of mercaptobenzothiazole land substantially one molecular proportlonof acetaldehyde-ammo'nia were placed in a. suitable 'vessel' and heatedslow-ly to'a'pproximately 130 to 1459C.) Substantially one-half a molecular proportion of" phthalyl chloride was thenaddedand the tem-' 'perature maintainedat approximately l15'to 130 C. for a suitable periodof time necessary to complete the reaction, preferably fora period of approximately one hour.': A portion of the product thus formed was compounded in a rubber stock comprising P1 and the mercaptobenzothiazole derivative of acetaldehyde-ammonia 1 The stock; was cured in the, usual manner and foundupontesting, to possess the characteristics set: forth in Table VIII.

Table 'VIII 1 Modulus of elasticity in lbs/in at elongationsoi- Tensile 1 atbreak Om Ulti- 1 mate 7 elongation percent Steam 5 pressure lbs.

Time

IIllHlIIl- 30 a0 g 45' 30 r This accelerator was also employed in conjunction with diphenylguanidine in the following rubber mix: a 115 Parts Zinc oxide j 5 Sulfur 7 '3 Diphenylguanidine The reaction product; of

and the mercaptobenzothiazole derivative of acetaldehydeeammonian' a 0.8

' The rubber stock formed was cured and the vulcanized product subm itted to physical tests.

a The results rone in Table IX.

Table IX I L I Modulus of elasticity Cure "in lbs/in at elouga- .IiOnS 0fv 1 Tensile I elongasteam lbs/i11 .135 '..-?F...?.Z 5 3 0 700% 50 30 300 50s I ,2000 4200 s00 45 30 353 840 3105 4595 785 60 30 362 847, 3285 4725 780 The data set forth in Tables VIIIand IX show that the reaction product of phthalyl chloride and 5 the mercaptobenzothiazole derivative of acetaldehyde-ammonia possesses valuable accelerating properties when employed in the rubber vulcanization process 'The'se accelerating properties are greatlyincreased'in the presence of a basic, or-t ganic nitrogen-containing activator accelerator.

' Another example 4 of 'the" preferred new class' 1'50 derivative of a reaction product of butyraldehyde and ammonia, was prepared-as follows. Substantially ,three molecular proportions of butyraldee hyde were :treated withgaseous ammonia until no -morewas absorbed. The oily product'was separated from the'water formed by the-reaction,

and the former was further treated with substantially .one, molecular proportion of mercaptobenzothiazole by heating the reactants together-at approximately 55 to C. for a short period of time, for example, approximately ten minutes. Substantially one molecular proportion of benzoyl chloride was slowly added while agitating and maintaining the temperature of the mixture at approximately 80 to 90 C. This temperature was maintained, after the addition of benzoyl chloride had been completed, for a suitable period of time necessary to complete the reaction, for example, for a period of approximately one hour.

' 'A portionof the product thus formed was incorporated in'a rubber stock of the following composition:

The benzoyl chloride reaction product of the mercaptobenzothiazole derivative of the reaction product of butyraldehydeand'ammonia, prepared as described above 1 The compounded rubber stock was curedin the usual manner, and the resulting product tested to determine its physical characteristics. The results are setforth in Table X.

Table X.

Modulus of elasticity v -Cure in lbs/in at elongations l Tensile o I V atlirneak elgngav S eam H, lbs/in v 1 M minutees pressure 300% 500% 700% I pement The above results showthat the accelerator V triheptylidene-diamin'e, (CvHm) sNapreparedf-rom substantially three molecular proportions of heptaldehyde and substantially two molecular pro-'- portions of ammonia, was treated in a suitable 'vessel with substantially one molecular proportion of mercaptobenzothiazole while maintaining the reaction temperature at approximately to C; until reaction was complete. Substantially one-half a molecularproportionof phthalyl. 1 chloride was added slowly while maintaining the temperature at approximately 80 to 901C. temperature was maintained for asuitable period necessary to complete the reaction,- after all the phthalyl chloride had been added, preferably for a period of, approximately one hour; A portion of the product thus formed was incorporated in the usual mannner in a rubber mix comprising ,Parts Pale crepe rubber 100 Zinc oxide. i 5 Sulfur 3 Stearic acid 1" tests. The results are set forth in Table XI.

T able XI hgodu lue 01f elast ticity llfl V s/m a e onga 1011s 0 Tensile Um: batk inate rea e onga- Time fg f in tion min- 7 300% 500% 700% lbs/in percent utes 1 7 lbs.

30 30 381 N 974 3865 5225 f 780 4 30v 8 1 760 The results given in Table XI show that the accelerator employed possesses very" desirable properties wheirused in a rubber mix of vulcanization characteristics.

Another example of the preferred class of com pounds, comprising areaction productof phthalyl chloride and the piperidine salt or mer captobenzothiazole, was preparedv as follows; Substantially one molecular proportion or phthalylchloride was added to substantially two molecular proportions of the piperidine salt of mercaptobenzothiazole in a suitable vessel. After all the phthalyl chloride had been added, the temperature of the mixture was maintained atapproximately to C. fora periodof time sufiicient tocomplete'the reaction, preferably for approximately one hour. A portion of the product hus formed waslcom po unded in a rubber stock comprising.

I Parts Pale crepe rubber 100 Zinc oxide are: 7 5v Sulfur"; 3" steariQ acid o The reaction product of phthalyl chlorid and the piperidine salt of merca'ptoben zothiazol'e 0175 After vulcanization, the rubber stoclt thus formed was tested and found to possess the following modulus and tensile characteristics:

Table XII Modulus ofelasticityin Cure lbs 111 t el at ons i a (mg 0 Tensile Ultim a: i

, rea e o -'lime' E??? N 1 in ga'tion m m 300% 500% 700% lbs/in percent utes l lbS; I r l .30; 1 a0 a 255; 57szero 1 4095' 790 45 3o 248 697 $3125] 41300 7 55 '60 -30 300 731" 3220 l 4525 I 760 messa e These data show that the accelerator employed possesses the valuable properties of the preferred class of compounds. 7

Another of the preferred class of accelerators,

for example, a reaction product of benzoyl chlo' ride and the piperidine salt of mercaptobenzothiazole, was prepared as follows: Substantially one molecular proportion of benzoyl chloride was added. slowly to substantially onev molecular proportion or the piperidine salt of mercaptoben zothiazole, preferably in the presence of a'liquid medium, for examplegbenzol. The mixture was preferably maintained at a refluxing temperature for a short period after all the 'benzoyl chloride had been added. The liquid medium employed was then removed by any convenient means, as

for example by distillation under subatmospheric pressure. A portion of the material thus prepared was incorporated in a rubber stock.comp isi I I. Parts Pale"crepe rubber s 100,

Zinc oxide 5 Sulfur 3 Stearic acid 1 The reaction product of benzoyl chloride and the piperidine salt of mercaptobenzothiazole 0.75

The stockthus formed wasl cured and the V111 canized rubber product tested for physical characteristics. The results are as follows:.,

Table. XIII Cure Mogugui ogelast ifltyi l L I l lbs, 11 a e onga ionso Tentsfle Ultth a mae steam me a break elon- Time in gatlon ming ;300% 700% ,lbs /in percent 9?, lbs.

3o 30 isz 2175 53880 820 45 30 214 2645 v 4180 800 60 30 275 2900 4435 790 The results set forth in Table XIIIshow thatthebenzoyl chloride reaction product of the piperidine salt of mercaptobenzothiazole' possesses the desirable accelerating properties'of the preferred class of compounds.

Another of the preferred bless of accelerators, for example, a reaction product of phthalyl chloride and a mercaptobenzothiazole salt of para-para-diamino-d phenylmethane, was prepared as follows: Substantially onemolecular proportion of phthalyl chloride was added slow-l 1y to substantially two molecular proportions'of the salt formed by reacting substantiallyequal molecular proportions of mercaptobenzothiazole and para-para-diaminodiphenylmethane, while agitating. Any "liquid vaporizing: in the process wasretained by means of a reflux condenser.

After the phthalyl chloride had been added, the mixture was preferably heated at approximately to C. for a period sufilcient to complete the reaction, preferably for approximately two hours. A portion of the product thus prepared was'compoundedin a rubber stock of the following composition:

The reaction product of phthalyl chloride;

and the mercaptobenzothiazole ":salt o1 para-para-diamino-diphenylmethane V 1 The stock thus-formed was cured theusual manner andthe vulcanized fproduct tested. to determine itsmodulus and tensile properties. The results are as follows: I

Table XIV. V i

b rioqu iue elest i it ni 5 bs/ln ate ongalons of Tensile Um; batk {hate j I ma eonga Time W3 in tion minga 300% 500% 700% lbs/in percent utes I lbs.

30 30 154 37s 1540 3510 45; i' so 486 11900 3640 ;s 0, so 229 543 2125 382.5

I This ac'cele'rator was, also ernployedinconjunc tion with diphenylguanidine the following .rubr ber mix: U f- I ."Parts 100 Pale creperubber The rubber stockthus prepared cured and the vulcanized product tested in the usualman-- ner.,- The results followin Tabl e I The-results f-the varioustests described above show conclusively that the preferredcla'ss ofmaterials constitutesan important new class? of accelerators forQthe -rubber. vulcanization process. In like mannenother organic; bases may be reacted with a mercaptoarylthiazole, and the re sulting products may {be further. reacted with .orf ganic acid halides to form further examples of the preferred new. class of accelerators. Thus, diphen-ylguanidine, -ethylideneaniline, d'iethylamine,-,diben zylamine, triethanolam ine, 2' *l-di aminodiphenylamine, paraephenylenediamine,

hydro-formaldehyde-aniline, the reaction, product of crotonaldehyde and the mercaptobenzo thiaz ole derivative of hexa rnethylene tetramine, and -the lilre',form double salt lilre compounds when reacted with mercaptobenzothiazole, mercaptotolylthiazole, mercaptonaphthothiazoles,

. and the like, and the products thus formed may be 5 further reacted with acetyl, chloride, acetyl bromide, succinyl chloride; benzoyl chloride, phthayl chloride heptoyl chloridebenzoyl iodide,

and the like, and theflnal products formed employed'as-accelerators in the rubbervulcani'zation process; v

In theabove described examples of the use of the preferred class of accelerators, dipheny-l u nidin was-em e as the re err d.

vator in thosefcases wherea mixedaccelerator' was employed: Other accelerators. comprising tion as broadly as ispermissible in view of the prior art. 7

What is claimed is:

1. The process of vulcanizing rubber which comprises heating rubber and sulfur in the presence of an accelerator comprising a reaction prodnot of an organic acid halide and a mercaptoaryl thiazole derivative of an organic base.

2. The process of vulcanizing rubber which-- comprises heating rubber and sulfur in the presence of an accelerator comprising a reaction product of an organic acid halide and a mercaptobenzothiazole derivative of an organic base.

3. The process of vulcanizing rubber which comprises heating rubber and sulfur in thepresence of an accelerator comprising-a reaction product of an organic acid chloride and a mercapto-' benzothiazole derivative of an organic base.

4. Th'e process of vulcanizing rubber which comprises heating rubber and sulfur in the pres ence of an accelerator comprising a reaction productof an organicv acid chloride and a mercaptobenzothiazole derivative ofa reaction product of an aldehyde and ammonia.

5. The process of vulcanizing rubber which comprises heating rubber and sulfur in thepresence of an accelerator comprising a reaction prod- 1 not of an organic acid chloride and amercapto- 40" benzothiazole derivative of areaction product of an aliphatic aldehyde and ammonia.

a 6. The process of vulcanizing rubber which comprises heating rubber and sulfur in the presence of an accelerator comprising'a reaction product of an organic acid chloride anda mercaptobenzothiazole'derivative of an organic amine.

' 7. The process of vulcanizing rubber which comprises heating rubber and sulfur in the presence of an accelerator comprising a'reaction' product of an organic acid chloride and a-mercapto- ,benzothiazole' derivative of an organic tertiary amine.

8.The process of vulcanizing; rubber which comprises heating rubber and sulfur in the'presence of an accelerator comprising a reaction product of an organic acid chlorideand a mercapto- -benzothiazole derivative of "heXa-methylenetetramine. a Y 1 9. The process of vulcanizing rubber which comprises heating rubber and sulfur 'in'the presence of an accelerator comprising a reaction product of an aromatic acid chloride and a mercaptobenzothiazole derivative of *hexa-methylenetetramine. 7 V 10. The process of vulcanizing rubber which comprises heating r'ubber'and sulfur in the presence of an accelerator comprising a reaction prod-- not of an aromatic acid chloride containing a singlebenzne' nucleus and-a mercaptobenzothiazole derivative of hexa-methylene-tetramine. 11. The process'of vulcanizing rubber which comprises heating rubber and sulfur in the presence of an accelerator comprisin'ga reaction prod.-

- uct of phthalyl chlorideand a-mercaptobenzo-' thiazole derivative of hexa-methylne tetramine;

121Th process of vulcanizing rubber whi'ch comprises heating rubber and sulfur inthe presence of an accelerator comprising a' material formed by reacting substantially one'mole'cular proportion of hexa-methylene-tetramine' with substantially one and one-half molecular propor-' comprises heating rubber and sulfur in the pres ence of a mixed accelerator comprising a basic organic nitrogen-containing accelerator and a reaction product of an organic acid chloride and a mercaptobenzloithiaz ole derivative of a reaction product of an aliphatic aldehyde and ammonia. 15.'The process of vulcanizing rubber which comprises heating rubber and sulfur in the presence of a mixed acceleratorcomprising a basic V organic nitrogen-containing accelerator and a a reaction product of anorganic acidchloride and" a mercaptobenzothiazole derivative of .hexamethylene-tetramine.'

16. The process of'vulcanizing rubber which comprises heating rubber and sulfur in the presence of a mixed accelerator comprising diphenylguanidine and a reaction product of phthalyl chloride and a mercaptobenzothiazole' derivative of hexaemethylene-tetramine.

17; The vulcanized rubber produced by heating rubber and sulfur in the presence of'an accelera tor comprising a reaction product'of an organic acid halide and ajmeroaptoarylthiazolederivative of an organic. base." g

18. The vulcanized rubber produced by heating .rubber and sulfur in the presence of an accelerator comprisinga reaction product of an .organic acid halide and a mercaptobenzothiazole derivative of an organic base. 1 I

19. The vulcanized rubber producedby heating rubber and sulfur in the presence of an accelerator-comprising a reaction product of an organic. acid chloridejand a mercaptobenzothiazole .derivative of an organic base. V a

20. The vulcanized rubber produced by heating rubber and sulfur in the. presence of an accelerator comprising a'reaction product of an organic acid chloride and a mercaptobenzothiazole derivative of a reaction product of an aldehyde and ammonia. w V g 21. The vulcanizedrubber produced by heating rubber and sulfur in the presence of an accelera tor comprisinga reaction product. of an organic acid chloride and a mercaptobenzothiazole derivative of a reaction product of an aliphatic aldehyde and ammonia.

22. Thevulcanized rubberproduced by heating rubber and sulfur in the presence of an accelerator comprising a reactionproduct of an organic acid chloride'and a mercaptobenzothiazole derivative of an organic amine.

23. The vulcanized rubber produced by'heatin rubber and sulfur in the presence of an accelerator comprising a reaction productof an organic acid chloride and a mercaptobenzothiazole derivative of "an organic tertiary amine..

' 2s. The vulcanized rubber produced by heating methylene-tetramine.

27. The vulcanized rubber produced by heating rubber and sulfur in the presence of an accelerator comprising a reaction product of phthalyl chloride and a mercaptobenzothiazole derivative of hexa-methylene-tetramine. 7

28. The vulcanized rubber produced by heating rubber and sulfur in the presence of an accelerator comprising a material formed by reacting substantially one molecular proportion of hexamethylene-tetramine with substantially one and one-half molecular proportions of 'mercaptobenzothiazole and further reacting the product thus formed with substantiallyone-half a molecular proportion of phthalyl chloride.

29. The vulcanized rubber produced by heatin rubber and sulfur in 'thepre'sence of a mixed accelerator comprising a basic organic nitrogen- I containing accelerator and'a reaction product of an organic acid chloride and a mercaptobenzothiazole derivative of an organic base.

30. The vulcanized rubber produced by rubber and sulfur in the presence of, a mixed acheating celerator comprising -a basic organic nitrogen-'v containing accelerator and a reaction product of an organic acid chloride and a mercaptobenzothiazole derivative of a reaction product of an aliphatic aldehyde and ammonia. c

31. The vulcanized rubber producedby heating rubberand sulfur in the presence of a mixed accelerator comprising a basic organic nitrogencontaining accelerator and a reaction product of an organic acid chloride and a mercaptobenzothiazole derivative of hexa-methylene-tetramine, 32. The vulcanized rubber produced by heating rubber and sulfur in the presence of a mixed accelerator comprising diphenyl-guanidine and a reaction product of phthalyl chloride and a mercaptobenzothiazole derivative of hexa-methylenetetramine.

- ROBERT L. SIBLEY, 

